The present invention is directed toward an improvement in a chemical vapor deposition reactor, such as the UNIPAK and MINIPAK reactor systems manufactured and sold by Unicorp, Incorporated of Sunnyvale, California, the assignee of the present application. Such a reactor provides a quartz tube within a radio frequency coil. Silicon wafers to be processed are carried by a graphite susceptor within the reactor tube. When the coil is energized with a source of radio frequency energy, eddy currents are generated in the susceptor, thus causing it and the silicon wafers thereon to become heated. The gaseous atmosphere within the reactor tube is controlled to contain desired materials which chemically react with the heated silicon surface to form layers of material thereon.
The inside surface of the quartz reactor tube also becomes coated with gaseous material depositing thereon. This coating results from the reactor tube walls themselves becoming heated during the processing of wafers to a temperature sufficient to cause deposition thereon. As the deposition layer on the tube increases in thickness, it eventually begins to peel and chip off and is a large source of impurities in the resulting semi-conductor product. To avoid such impurities, the reactor tube must frequently be removed for thorough cleaning of its inside surface. Only 2 or 3 batches of semi-conductor wafers can be processed with common techniques between cleanings. This frequent cleaning is required even though a fan of ordinary design is provided on the outside of the reactor tube for cooling.
Therefore, it is a primary object of the present invention to provide an improved chemical vapor deposition reactor product and process that results in a reduced cleaning requirement of the inside of the reactor tube.